An electronic ear

doi:10.1038/nindia.2017.150 Published online 5 December 2017

Using a novel "sequential elemental de-alloying"
technique to make porous metal oxides, researchers at the Indian
Institute of Science (IISc) in Bengaluru have fabricated a humidity sensor that
doubles as an electronic ear1.

Highly porous materials, with variable chemical compositions
belong to the family of 'functional' materials used for making
devices capable of reproducing human senses. The electronic nose is one such device.

The IISc's humidity sensor based on porous stannic oxide (SnO2) can measure
changes in relative humidity with an accuracy of 1% — a property that will
enable online monitoring of hospitalised patients of asthma, cancer, diabetes,
and dehydration by measuring the humidity changes between their inhaled and
exhaled breath.

According to the researchers, their humidity sensor responds
distinctly towards speaking, breathing, and whistling. It is able to recognise
and create a distinct response pattern for words spoken by different users
indicating its potential to differentiate between words like the human ear.
The observed abilities of the sensor "will facilitate its utilisation for
electronic listening as well as for biomedical applications," says the
report.

Besides, the two-step strategy developed for the synthesis of
three-dimensional porous SnO2 microstructures "can be applied to fabricate
other porous metal oxides also."